Other common autofocus problems
Despite all its advancements, autofocus technology is still loaded with problems. One of the biggest limitations of cheaper cameras is that they only offer a single, centre-frame AF point. Speed is another issue, even with entry-level DSLRs, although by pre-focusing or panning you can capture predictable fast-moving subjects.
Moreover, with the exception of pro DSLRs, most continuous- servo modes are far less effective than their propaganda suggests, eating up battery power extremely fast.
Another acute problem, particularly with digital compact cameras, is noise, which renders many cameras useless for wedding, wildlife and candid photography.
You may also find that your autofocus mechanism becomes sluggish when the working temperature becomes significantly colder or hotter than room temperature. Even cutting edge professional AF systems aren’t foolproof – note the classic situations when they fail above.
If you can’t focus properly, first try your camera’s AF lock facility. Focus on something else exactly the same distance away as your desired subject and activate the lock.
Keeping the shutter button half depressed, recompose the photo correctly and depress the shutter button fully. Most cameras let you control whether the exposure and focus are locked simultaneously or separately.
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